US20100130983A1

Movatterモバイル変換

Info

Publication number: US20100130983A1
Application number: US12/324,142
Authority: US
Inventors: Lisa R. Thornhill; Viorel Mocanu
Original assignee: Osteomed LLC
Current assignee: Osteomed LLC
Priority date: 2008-11-26
Filing date: 2008-11-26
Publication date: 2010-05-27
Also published as: WO2010062634A1

Abstract

A system for establishing a trajectory for a pilot hole includes a plate comprising a screw hole defined by a rim and an inner surface surrounding the screw hole, and a drill guide comprising a body having a guide well formed therein, the guide well defined by a wide opening in the body disposed opposite a narrow opening in the body and an interior surface that tapers from the wide opening to the narrow opening, the narrow opening surrounded by a tip of the body, the tip configured to fit into the screw hole.

Description

TECHNICAL FIELD

The present disclosure relates generally to repairing bone fractures, and more particularly, to a drill guide for angled trajectories.

BACKGROUND

When repairing a broken, fractured, or shattered bone, a physician may often be faced with the task of affixing a fixation plate to the bone in order to align the bone, and possibly, to hold bone fragments together. In order to affix the fixation plate to the bone, the surgeon may screw a bone screw into a predrilled pilot hole in the bone through one of a plurality of screw holes in the fixation plate. Since numerous screw holes may be spread out across the entirety of the fixation plate, the surgeon may affix virtually any portion of the fixation plate to the bone by inserting a suitable number of bone screws through the fixation plate and into the bone.

To prevent the bone screws from backing out of the fixation plate once inserted, the inner surface of each screw hole may include a set of locking threads configured to interfere with a corresponding set of locking threads on the head of each bone screw. Consequently, when a bone screw is screwed into one of the threaded screw holes in the fixation plate, the locking threads in the screw hole and/or the locking threads on the head of the bone screw may deform to lock the bone screw into the fixation plate.

In certain cases, proper placement and positioning of the fixation plate may call for inserting a bone screw into the fixation plate at an angle other than parallel to the central axis of the screw hole. For example, if the underlying bone beneath a particular screw hole is weak, for example, due to its proximity to a fracture line, the surgeon may wish to angle the bone screw away from the fracture line so as to anchor the bone screw into a more solid bony mass. In another scenario, the surgeon may wish to avoid a nerve underlying the screw hole.

SUMMARY

In particular embodiments, the present disclosure provides for a system and method for establishing a trajectory for a pilot hole. The system may include a plate having a screw hole. The screw hole may be defined by a rim and an inner surface surrounding the screw hole. The system may further include a drill guide comprising a body having a guide well formed therein. The guide well may be defined by a wide opening in the body disposed opposite a narrow opening in the body and an interior surface that tapers from the wide opening to the narrow opening. The narrow opening may be surrounded by a tip of the body that is configured to fit into the screw hole.

A method for establishing a trajectory for a pilot hole may include placing a plate onto a bone, the plate including a screw hole defined by a rim and an inner surface surrounding the screw hole. The method may further include fitting a drill guide into the screw hole, the drill guide comprising a body having a guide well formed therein. The guide well may be defined by a wide opening in the body disposed opposite a narrow opening in the body and an interior surface that tapers from the wide opening to the narrow opening. The narrow opening may be surrounded by a tip of the body that is configured to fit into the screw hole.

In particular embodiments, the method may further include inserting a drill bit into the guide well and drilling a pilot hole into the bone while keeping the drill bit within the confines of the interior surface.

Technical advantages of particular embodiments of the present disclosure may include providing a system and method for enabling a surgeon to effectively judge the maximum angle of insertion for which the locking effect between a locking bone screw and a locking fixation plate will be maintained. This technical advantage may be realized through the use of a drill guide placed on the fixation plate that physically defines the maximum angle of insertion, giving the surgeon a defined range of acceptable angles within which to drill a pilot hole. The drill guide may further include a tip that fits securely into the screw hole of the fixation plate to align the drill guide with the screw hole and to protect the threading inside the screw hole from the drill bit during creation of a pilot hole, yet another technical advantage.

Other technical advantages of the present disclosure will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and its advantages, reference is now made to the following descriptions, taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a system for establishing a trajectory for a pilot hole according to an example embodiment of the present disclosure;

FIG. 2 illustrates an isometric view of an example embodiment of a fixation plate according to an example embodiment of the present disclosure;

FIG. 3 illustrates an isometric view of an example embodiment of a drill guide according to an example embodiment of the present disclosure; and

FIG. 4 illustrates an example cross section view of a portion of the drill guide ofFIG. 3 exposing a more detailed view of the interior surface of the drill guide.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Various fixation plates may include specially designed screw holes that may lockably engage a bone screw inserted (e.g., “screwed in”) along a trajectory other than parallel to (e.g., coaxial with) the central axis of such screw holes. In one example embodiment, the bone screw may include threading on the underside of the head that interferes with threading inside the screw hole to lock the bone screw into the fixation plate once the bone screw is screwed into the screw hole.

To facilitate insertion of the bone screw into the screw hole along an angled trajectory, a pilot hole may be drilled into the bone to establish the trajectory for the bone screw. After the pilot hole has been created, the tip of the bone screw may be inserted into the pilot hole through the screw hole in the fixation plate and rotated until the threaded portion on the underside of the head comes to bear on the threaded portion of the screw hole. At this point, further rotation of the bone screw may cause the threaded portion of the head to interfere with the threading inside the screw hole and lock the bone screw into the plate.

Depending upon design, the above-described locking effect between the bone screw and the fixation plate may only be effective up to a maximum angle of insertion of the bone screw relative to the central axis of the screw hole. If the trajectory of the bone screw exceeds the maximum angle of insertion, the locking effect may become unreliable or may fail, increasing the propensity of the bone screw to back out of the screw hole. In other words, depending upon design, the screw hole in the fixation plate may only be able to accommodate a certain angular range of screw engagement before the locking mechanism is weakened or rendered inoperable.

In the operating room, a surgeon may not be able to effectively judge the maximum angle of insertion by visual inspection and may need a tool to help him drill a pilot hole within the specified limits of the plate design (e.g., within the maximum angle of insertion). Consequently, there is a need for a system and method to reliably establish the trajectory for the pilot hole within the maximum angle of insertion and also a need to protect the threading inside the threaded screw hole from being deformed by the drill bit during creation of the pilot hole.

FIG. 1 illustrates asystem100 for establishing a trajectory for apilot hole102 according to an example embodiment of the present disclosure.System100 generally includes adrill guide104 for guiding adrill bit106 and afixation plate108 for affixing portions of abone110 together and for holdingdrill guide104 steady relative tobone110.

In the pictured embodiment,system100 is being used relative to a single fracturedbone110; however, particular embodiments ofsystem100 may be applied equally as well to virtually any bone or group of bones in the body.System100 may also be used to create apilot hole102 in a synthetic element such as a surgical implant.

To establish the trajectory forpilot hole102 usingsystem100, a surgeon may placefixation plate108 ontobone110, after which the surgeon may fit the tip112 (seeFIG. 3) ofdrill guide104 into any one of a plurality ofscrew holes114 disposed throughoutfixation plate108. In particular embodiments, the surgeon may temporarily or permanently securefixation plate108 onbone110 using pins,bone screws116, or other suitable means while creatingpilot hole102. In any case, once thetip112 ofdrill guide104 has been inserted into ascrew hole114, the surgeon may createpilot hole102 by insertingdrill bit106 into a guide well118 indrill guide104 and drilling intobone110 within the confines of guide well118.

If the surgeon is using abone screw116 having a locking feature,drill guide104 may be used to ensure that the angle ofinsertion120 for bone screw116 (e.g. the trajectory ofpilot hole102 relative to thecentral axis122 of screw hole114) is less than or equal to the maximum angle ofinsertion124 for which the desired locking effect betweenbone screw116 andfixation plate108 will be preserved. For example,drill guide104 may designed such that, once thetip112 ofdrill guide104 has been positioned in ascrew hole114, the aperture angle126 (seeFIG. 4) of guide well118 is coextensive with the twice the maximum angle ofinsertion124. One of ordinary skill in the art will appreciate thataperture angle126 is coextensive with twice maximum angle ofinsertion124 whenaperture angle126 is twice as large as maximum angle ofinsertion124 since maximum angle ofinsertion124 is measured with respect tocentral axis122 whileaperture angle126 is measured with respect to opposing sides of guide well118. Consequently, by drilling within the confines ofdrill guide104, the surgeon may be assured that the angle ofinsertion120 established forbone screw116 is less than or equal to the maximum angle ofinsertion124. Oncepilot hole102 has been created usingdrill guide104,fixation plate108 may be affixed tobone110 byscrewing bone screw116 intopilot hole102 throughscrew hole114.

Depending upon design,drill guide104,bone screw116, andfixation plate108 may be formed from any one or more materials suitable for forming medical devices and implants, such as materials that have high strength-to-weight ratios and that are inert to human body fluids. In certain embodiments,drill guide104,fixation plate108, orbone screw116 may be formed from one or more titanium alloys, which provide several benefits. For example, titanium alloys are relatively lightweight, provide adequate strength for withstanding high forces, are inert to human body fluids, and are visible in radiographs. In particular embodiment,bone screw116 may be formed from the titanium based alloy Ti6Al4V ELI (per ASTM F136), which provides a desirable combination of benefits, such as those discussed above whilefixation plate108 may be formed from grade 2 or grade 3 titanium (per ASTM F67). In certain other embodiments,bone screw116 orfixation plate108 may be formed from one or more resorbable polymers, such as polylactides, polyglycolide, glycolide/lactide copolymers or other copolymers for example, or one or more implantable plastics, such as polyethylene or acetal copolymers for example.

One of ordinary skill in the art will appreciate that the above-described embodiments ofsystem100 were presented for the sake of explanatory simplicity and will further appreciate that the present disclosure contemplates using any suitable combination andnumber locking screws116 andfixation plates108 to repairbone110.

FIG. 2 illustrates an isometric view of an example embodiment offixation plate108. For reference purposes, fixation plate108 (as well as other components of system100) may be referred to as having a bottom side intended to be placed closest to bone110 (e.g., to be placed upon bone110) and a top side intended to be place furthest frombone110. Though particular features offixation plate108 may be explained using such intended placement as a point of reference, this method of explanation is not meant to limit the scope of the present disclosure to any particular configuration offixation plate108 or to any particular placement or orientation offixation plate108 relative tobone110 or any other components ofsystem100.

Fixation plate

108 may typically be any fixture including one or more screw holes114 for receiving abone screw116. In the pictured embodiment,fixation plate108 generally includes a plurality of screw holes114 connected to each other in a web-like distribution by a plurality ofribs128. Eachscrew hole114 may include a rim130 (e.g., a flat surface surrounding screw hole114). Though in the pictured embodiment,ribs128 are thinned down relative to eachrim130, particular embodiments ofplate108 may be designed such that the entirety ofplate108 is uniform in thickness. In any case, whendrill guide104 is fitted into ascrew hole114,rim130 may rest flush against theshoulder132 ofdrill guide104, providingdrill guide104 with a steady foundation onfixation plate108.

To aid a surgeon inpositioning fixation plate108 relative tobone110, one ormore ribs128 may comprise apositioning hole134. As an example and not by way of limitation, a surgeon may insert a K-wire intobone110 after which the surgeon may positionfixation plate108 onbone110 by inserting the K-wire throughpositioning hole134 and slidingfixation plate108 down ontobone110. Additionally, the surgeon may rotatefixation plate108 about the K-wire usingpositioning hole134 to achieve a desired orientation offixation plate108 relative tobone110. Oncefixation plate108 has been properly positioned, the surgeon may usedrill bit106 in conjunction withdrill guide104 to create apilot hole102 throughscrew hole114. The surgeon may then securefixation plate108 tobone110 by screwingbone screw116 intoscrew holes114 along the trajectory established bypilot hole102.

Eachscrew hole114 may be any an opening infixation plate108 configured to accept abone screw116. In particular embodiments, the inner surface of eachscrew hole114 may be threaded to lockably engagebone screw116 such that oncebone screw116 has been screwed intoscrew hole114,bone screw116 is prevented from rotating withinscrew hole114. As mentioned above, to accomplish this locking feature, the underside of the head ofbone screw116 may include a locking thread configured to interfere with the threading insidescrew hole114. Thus, whenbone screw116 is screwed intoscrew hole114, the locking thread on the head ofbone screw116 may deform against the threading insidescrew hole114 to lockbone screw116 intofixation plate108.

In particular embodiments, screw holes114 may be designed to enablebone screw116 to be screwed in along a trajectory other than parallel tocentral axis122 while still maintaining the ability to lockably engagebone screw116. One example system for achieving an angular locking interface between a bone screw and a fixation plate is described in U.S. Provisional Application 61/106,511, entitled “ANGULATED LOCKING PLATE/SCREW INTERFACE,” filed Oct. 17, 2008.

In particular embodiments, design constraints or other considerations may limit the range of insertion angles for which the locking effect betweenbone screw116 andfixation plate108 remains viable. For example, a manufacturer may designfixation plate108 such that the locking interface betweenbone screw116 andfixation plate108 remains viable for insertion angles up to ten degrees from parallel thecentral axis122 ofscrew hole114. Beyond this ten degree radius aroundcentral axis122, the locking effect brought about by the threadable interface betweenbone screw116 andplate108 may be unreliable; for example, the amount of contact between the threading onbone screw116 and the threading insidescrew hole114 may be insufficient to overcome the mechanical forces that may causebone screw116 to back out ofscrew hole114. Consequently, the maximum angle ofinsertion124 in this example situation is ten degrees. One of ordinary skill in the art will appreciate that the maximum angle ofinsertion124 may be defined by the manufacturer according to any suitable criteria. For example, maximum angle ofinsertion124 may be defined as the angle beyond which a certain percentage of locking failures occur at a give stress level. In the operating room,drill guide104 may enable a surgeon to effectively judge the maximum angle ofinsertion124 when drilling apilot hole102 forbone screw116 by providing a physical barrier that physically defines maximum angle ofinsertion124 for the surgeon. Consequently, by drilling within the confines ofdrill guide104, the surgeon may be assured that the trajectory ofpilot hole102 will be less than or equal to the maximum angle ofinsertion124.

One of ordinary skill in the art will appreciate that the above-described embodiments offixation plate108 were presented for the sake of explanatory simplicity and will further appreciate that the present disclosure contemplates any suitable configuration forfixation plate108.

FIG. 3 illustrates an isometric view of an example embodiment ofdrill guide104. Depending upon design,drill guide104 may generally include a funnel-shapedbody136 rigidly coupled to ahandle138.Body136 may have a guide well118 formed therein that is defined by awide opening138 at the top ofbody136, anarrow opening140 at the bottom ofbody136, and an interior surface142 (seeFIG. 4) that uniformly tapers (e.g., tapers in diameter) fromwide opening138 tonarrow opening140. In particular embodiments,wide opening138 andnarrow opening140 may be concentric circles disposed opposite one another onbody136.Body136 may further include atip112 that surroundsnarrow opening140 and ashoulder132 disposed abovetip112 that includes a flat underside configured to rest flush againstrim130 whentip112 is inserted into ascrew hole114.

In particular embodiments,drill guide104 may be fitted intofixation plate108 by slidingtip112 intoscrew hole114 untilshoulder132 rests flush against the top surface of fixation plate108 (e.g., the top surface of rim130). To keeptip112 from wobbling around inscrew hole114, the outer surface oftip112 may be generally cylindrical in shape and sized to fit securely (e.g., snugly) intoscrew hole116. In particular embodiments, the outer surface oftip112 may be threaded to enable a surgeon to screwtip112 intoscrew hole116.Tip112 may be configured to align thecentral axis144 of guide well118 (seeFIG. 4) with thecentral axis122 ofscrew hole114. In particular embodiments, alength112L oftip112 may be approximately equal to thedepth114D ofscrew hole114 to protect the threading insidescrew hole114 from being deformed bydrill bit106 during the creation ofpilot hole102.

Shoulder

132 may be any fixture or combination of fixtures on the outer surface ofbody136 capable of providing a level footing forbody136 relative tofixation plate108. As an example and not by way of limitation,shoulder132 may comprise a contiguous smooth flatsurface surrounding tip112. Whentip112 is inserted intoscrew hole114,shoulder132 may abutrim130 and act as a stop that limits the penetration depth oftip112 intoscrew hole114, and as leveling mechanism thatlevels body136 relative tofixation plate108. As an example and not by way of limitation, the flat underside ofshoulder132 may be disposed perpendicular to thecentral axis144 of guide well118, thereby ensuring thecentral axis144 of guide well118 is parallel to (e.g., coaxial with) thecentral axis122 ofscrew hole114 whentip112 is inserted intoscrew hole114. Consequently, whendrill guide104 is fitted into ascrew hole114, the outer surface ofbody136 may be used to align andcouple body136 withfixation plate108 whileinterior surface142 may be used to limit the insertion angle ofdrill bit106 intobone110.

FIG. 4 illustrates an example cross section view of a portion ofdrill guide104 cut through thecentral axis144 of guide well118 to expose a more detailed view of theinterior surface142 surrounding guide well118. In particular embodiments,interior surface142 may be defined, in part, by a maximum diameter146 (e.g., the diameter of wide opening138), a minimum diameter148 (e.g., the diameter of narrow opening140), and anaperture angle126. Althoughaperture angle126 may be chosen according to any criteria, in particular embodiments, guide well118 may be designed such thataperture angle126 coincides with twice the maximum angle ofinsertion124 for which the locking effect betweenbone screw116 andfixation plate108 is preserved. Thus, ifaperture angle126 coincides with twice the maximum angle ofinsertion124,drill bit106 may be used to createpilot hole102 along virtually any trajectory within the confines ofinterior surface142 while still preserving the desired locking effect betweenbone screw116 andfixation plate108. As an example and not by way of limitation, if the maximum angle ofinsertion124 is approximately10 degrees measured from thecentral axis122 ofscrew hole112,aperture angle126 may be approximately20 degrees. Thus, oncedrill guide104 is fitted intoscrew hole114,drill bit106 cannot be inserted throughscrew hole114 along any trajectory greater than10 degrees fromcentral axis122 without wedging between the portion ofinterior surface142 surroundingwide opening138 and the portion ofinterior surface142 surroundingnarrow opening140.

In particular embodiments, to preventdrill bit106 from grinding against thebottom edge113 oftip112 during the creation ofpilot hole102, the portion ofinterior surface142 disposed insidetip112 may have a slight outward taper. In other words,interior surface142 may come to its narrowest point somewhere in the inside tip112 (e.g., at the uppermost portion of tip112) and then grow slightly wider before reachingbottom edge113. This outward taper may provide clearance fordrill bit106 to be inserted throughnarrow opening140 without grinding againstbottom edge113. In this case,narrow opening140 may refer to the narrowest point ofinterior surface142.

One of ordinary skill in the art will appreciate that the above described embodiments ofinterior surface142 were presented for the sake of explanatory clarification and will further appreciate that the present disclosure contemplatesinterior surface142 having any suitable size or shape. For example, althoughinterior surface142 was described and illustrated as having a generally circular base yielding a generally right angle conical shape,interior surface142 could just as easily have a generally square base yielding a generally pyramidal shape or any other geometrically suitable configuration operable to limit the insertion angle ofdrill bit106 intobone110.

Although the present disclosure has been described in several embodiments, a myriad of changes, substitutions, and modifications may be suggested to one skilled in the art, and it is intended that the present disclosure encompass such changes, substitutions, and modifications as fall within the scope of the present appended claims.

Claims

1. A system for establishing a trajectory for a pilot hole, comprising:

a plate comprising a screw hole defined by a rim and an inner surface surrounding the screw hole; and

a drill guide comprising a body having a guide well formed therein, the guide well defined by a wide opening in the body disposed opposite a narrow opening in the body and an interior surface that tapers from the wide opening to the narrow opening, the narrow opening surrounded by a tip of the body, the tip configured to fit into the screw hole.

2. The system ofclaim 1, wherein the drill guide further comprises a shoulder disposed adjacent to the tip, the shoulder comprising a flat surface configured to rest on the rim of the screw hole once the tip is fitted into the screw hole.

3. The system ofclaim 1, wherein a length of the tip is less than or equal to a depth of the screw hole.

4. The system ofclaim 1, wherein the tip is configured to align a central axis of the guide well with a central axis of the screw hole once the tip is fitted into the screw hole.

5. The system ofclaim 1, wherein the tip is configured to fit securely into the screw hole.

6. The system ofclaim 1, wherein the guide well is conical in shape.

7. The system ofclaim 1, wherein:

the inner surface of the screw hole includes threading configured to lockably engage a bone screw up to a maximum angle of insertion;

the interior surface of the guide well uniformly tapers according to an aperture angle; and

the aperture angle of the guide well is coextensive with twice the maximum angle of insertion of the screw hole once the once the tip is fitted into the screw hole.

8. The system ofclaim 1, wherein the drill guide further comprises an elongate handle coupled to the body.

9. The system ofclaim 1, wherein the wide opening is circular, the narrow opening is circular, and the wide opening is concentric with the narrow opening.

10. The system ofclaim 1, wherein a diameter of a portion of the interior surface disposed inside the tip grows wider as the interior surface extends toward an edge of the tip.

11. A drill guide, comprising a body having a guide well formed therein, the guide well defined by a wide opening in the body disposed opposite a narrow opening in the body and an interior surface that tapers from the wide opening to the narrow opening, the narrow opening surrounded by a tip of the body, the tip configured to fit into a screw hole of a locking plate, the screw hole defined by a rim and an inner surface surrounding the screw hole.

12. The drill guide ofclaim 11, further comprising a shoulder disposed adjacent to the tip, the shoulder comprising a flat surface configured to rest on the rim of the screw hole once the tip is fitted into the screw hole.

13. The drill guide ofclaim 11, wherein a length of the tip is less than or equal to a depth of the screw hole.

14. The drill guide ofclaim 11, wherein the tip is configured to align a central axis of the guide well with a central axis of the screw hole once the tip is fitted into the screw hole.

15. The drill guide ofclaim 11, wherein the tip is configured to fit securely into the screw hole.

16. The drill guide ofclaim 11, wherein the guide well is conical in shape.

17. The drill guide ofclaim 11, wherein:

the aperture angle of the guide well is coextensive with twice the maximum angle of insertion of the screw hole once the tip is fitted into the screw hole.

18. A method for establishing a trajectory for a pilot hole, comprising:

placing a plate onto a bone, the plate comprising a screw hole defined by a rim and an inner surface surrounding the screw hole; and

fitting a drill guide into the screw hole, the drill guide comprising a body having a guide well formed therein, the guide well defined by a wide opening in the body disposed opposite a narrow opening in the body and an interior surface that tapers from the wide opening to the narrow opening, the narrow opening surrounded by a tip of the body, the tip configured to fit into the screw hole.

19. The method ofclaim 18, wherein:

the drill guide further comprises a shoulder disposed adjacent to the tip, the shoulder comprising a flat surface configured to rest on the rim of the screw hole once the tip is fitted into the screw hole; and

fitting the drill guide into the screw hole comprises inserting the tip of the body into the screw hole until shoulder abuts the rim of the screw hole.

20. The method ofclaim 19, further comprising inserting a drill bit into the guide well and drilling a pilot hole into the bone within the confines of the interior surface.

21. The method ofclaim 20, wherein: